Seat assembly with coplanar parallelogram linkage

ABSTRACT

A spring seat assembly comprising a transversely extending seat support member, a transversely extending backrest support member spaced rearwardly therefrom, and sets of parallelogram arms on opposite sides of the assembly to interconnect the members. The assembly provides a unison action on displacement under load. The parallelogram arms lie in a common horizontal plane over the greater portion of their longitudinal lengths.

United States Patent Flint [451 Sept. 26, 1972 [54] SEAT ASSEMBLY WITH COPLANAR PARALLELOGRAM LINKAGE [72] Inventor:

Road, Orchard Lake, Mich. 48033 [22] Filed: Feb. 19, 1971 [21] Appl. No.: 116,848

[52] US. Cl ..297/309, 297/452 [51] Int. Cl. ..A47b 3/10, A47b 3/025 [58] Field of Search ..297/308, 309, 326, 349, 454,

[56] References Cited UNITED STATES PATENTS 3,512,831 5/1970 Flint ..297/309 3,517,964 6/1970 Flint ..297/309 Hyland C. Flint, 3551 Walnut Lake Reed ..267/86 Flint ..297/309 Primary ExaminerCasmir A. Nunberg Attorney-McGlynn, Reising, Milton & Ethington [57] ABSTRACT A spring seat assembly comprising a transversely extending seat support member, a transversely extending backrest support member spaced rearwardly therefrom, and sets of parallelogram arms on opposite sides of the assembly to interconnect the members. The assembly provides a unison action on displacement under load. The parallelogram arms lie in a common horizontal plane over the greater portion of their longitudinal lengths.

17 Claims, 5 Drawing Figures PATENTEDSP26 m2 SHEET 3 BF 3 ORNEYS SEAT ASSEMBLY WITH COPLANAR PARALLELOGRAM LINKAGE This invention relates to seats and particularly to the design of a unison action seat having a parallelogram arm linkage.

It is well known that a resilient, unison action seat may be provided by interconnecting a seat support element and a rearwardly spaced transverse member by means of a set of arms which define a parallelogram linkage. In this type of mechanism, the rear of the seat and the backrest are displaced in unison under load. In addition, the angularity of the backrest relative to a load-bearing surface remains substantially unchanged during displacement under load. Examples of such seats are shown in the H. C. Flint U.S. Pat. Nos. 3,261,642 and 3,512,831. I

The present invention bears an improvement relation to such previous inventions of H. C. Flint and provides a resilient, unison action type seat employing a parallelogram type linkage. However, in accordance with the present invention, the major portions of the longitudinal lengths of the parallelogram arms lie substantially in a common, horizontal plane. This geometric configuration differs markedly from the arrangements of the aforesaid Flint inventions and others wherein the parallelogram arms are substantially vertically spaced relative to one another.

The advantages which arise out of the present invention will be explained in detail with reference to the illustrative embodiments set forth in the following specification. However, by way of introduction to specific advantages which are found in the illustrative embodiments, it will first be observed that the subject seat exhibits an extremely shallow lateral profile, thus, to lend itself to incorporation in many mounting situations and arrangements including, as will be hereinafter described, a novel office chair base. In addition, the illustrative embodiment of the invention facilitates the interconnection of laterally extending spring elements such as sinuous wires between the longitudinally extending portions of the laterally spaced sets of parallelogram arms. In accordance with a preferred embodiment of the invention, the laterally opposite sets of parallelogram arms are formed as continuous U-shaped pieces of spring wirestock which are secured at the forward portion of the seat to a transverse seat support and pivotally connected at the rear of the seat assembly to a transverse backrest support.

The detailed description of the illustrative embodiment is given in the following specification which is to be taken with the accompanying drawings of which:

FIG. 1 is a front view of the illustrative embodiment of the invention;

FIG. 2 is a side view of the embodiment of FIG. 1 taken along a line of perspective 22;

FIG. 3 is a plan view of the embodiment of FIG. I viewed along aperspective line 3-3; 7

FIG. 4 is a side view of another illustrative embodiment of the invention incorporating an ofiice chair base; and,

FIG. 5 is a detailed view of a portion of the base arrangement of the embodiment of FIG. 4.

Referring now to FIGS. 1 through 3, there is shown a seat assembly 10 comprising atransversely extending seat support member 12, a transversely extending backrest support member 14, and, interconnecting the members 12 and 14, laterally spaced sets of resilient parallelogram arms 16, 18 and 20, 22. As can be detected from the side view of FIG. 2, the parallelogram arms 16, 18, 20, and 22 lie substantially in a common horizontal plane when in the unflexed no-load condition.

The seat support member 12 is fabricated from steel and is formed in the shape of a shallow pan having an upturned peripheral lip 24 around the front and laterally opposite sides thereof to add rigidity. The backrest support member 14 is similarly formed from sheet steel in the shape of a shallow pan having transversely extending back and bottom portions 26 and 28, respectively, joined by forwardly turned side panels 30 and 32.

Looking specifically to FIG. 3, it can be seen that the parallelogram arms 16 and 20 are formed from a single U-shaped piece of spring wire stock having any desired cross-sectional shape, but preferably being round. In addition, the parallelogram arms 18 and 22 are similarly formed from a single U-shaped piece of continuous spring wire stock. The forward ends of the parallelogram arms l6, 18, 20, and 22 are turned back on themselves so as to define loops 34, 36, 38, and 40, respectively, which lie in a common lateral line and which accommodate bolt and washer type fastener assemblies 42, 44, 46, and 48, respectively. The lateral central length of the spring wire stock which forms parallelogram arms 18 and 22 is of lesser dimension than the laterally extending central length of the stockforrning arms 16 and 20, thus, to permit the arms to lie nested in a common horizontal plane in the secured assembly as illustrated in FIG. 3.

Looking specifically to FIGS. 1 and 2 it can be seen that the parallelogram arms l6, 18, 20, and 22 lie in a common horizontal plane over the greater portion of the longitudinal lengths thereof but that at the rear portion of the arms 16 and 20, the spring wire stock is bent upwardly to form portions 50 and 52 which place the laterally extending center portion 54 between the arms 16 and 20 vertically above the corresponding portion of the spring wire stock which forms arms 18 and 22. The bent up portion 50 functions as a bendable release for any slight variation of arcing between the pivot points represented by elements 58 and 60. The vertically spaced relation between the intermediate connecting lengths of the spring wire stock from which the parallelogram arms are formed facilitates pivotal interconnection with the backrest support member 14 while at the same time providing a true parallelogram linkage between the members 12 and 14. As best shown in FIG. 2, a stamped steel support bracket 56 is welded into the interior area of the backrest support member 14 to receive a pair of upper retainer elements 58 and a pair of lower retainer elements 60. The upper retainer element 58 loop around and pivotally restrain the central length54 of the spring wire stock forming arm 16 and 20. The lower retainer element 60 similarly pivotally confined the intermediate length between the inner parallelogram arms 18 and 22. All of the elements 56, 58, and 60 are preferably formed of sheet steel and are welded in place. Although not shown in FIGS. 1 and 2, suitable bushings may be employed to improve the pivotal interaction between the spring wire stock and the retainer elements 58 and 60 on the backrest support member 14.

Completing the description of the seat portion of the assembly 10, reference to FIG. 3 shows a set of five S- shaped clips 62 secured to the parallelogram arms 16 and 18 at uniformly spaced positions, but in staggered relationship to the parallelogram arms; that is, the rearmost clip is attached to the arm 16 while the next clip is attached to the arm 18, the next to the arm 16 and so forth. In a similar fashion, clips 64 are disposed in staggered but uniformly spaced relationship along the pposite set of parallelogram arms 20 and 22. Between the laterally corresponding clips 60 and 64 are stretched spring elements 66 in the form of sinuous strip wire springs which define the primary seating area of the assembly 10. The spring element 66 are preferably of the pre-arched type which mustbe forcibly flatten out in order to be secured in position.

Looking now to the backrest portion 68 of the assembly 10, it can be seen in FIGS. 1 and 2 that a substantially U-shaped border wire 70 of flexible steel stock is disposed in a substantially vertical orientation with the opposite open ends thereof secured to the backrest support member 14 by way of retainers 72. A plurality of clips 74 are secured to the rear vertical wall 26 of the backrest support member 14't0 receive the lower end of sinuous wire spring elements 76 while clips 78 are secured to the cross member of the border wire 70 to receive the upper ends of the spring wire elements 76.

By way of an explanation of the operating theory of the assembly of FIGS. 1 through 3, the seat support member 12 is secured to a base, such as a furniture frame, an office chair base, an automobile floor, or such other support as is desired. The interconnection must, of course, provide sufficient vertical displacement clearance for the rear of the assembly 10, that is, the bottom of the backrest support member 14, to permit displacement thereof under load. An effective pivot point is provided at the rear edge of the seat support member 12, the distributed displacement or bending of the. spring wire parallelogram arms l6, 18, 20, and 22 occurring in the fashion of a cantilevered beam over the longitudinal lengths which extend rearwardly from the member 12. The vertical displacement between the pivotal connections between the cross portions of the parallelogram arms and the backrest support member 14 provides a parallelogram action wherein the vertical displacement of the rear of the seat is accompanied by a corresponding vertical displacement of the backrest 68, but during such displacement the angularity of the backrest 68 relative to the base or support surface, is substantially unaffected. In other words, the pivot points defined by retainers 58 and 60 remain substan tially vertically aligned.

Referring to FIGs. 4 and 5, an embodiment 100 of the invention is shown to comprise the assembly 10 of FIG. 2 carried by an ofiice chair type base 102 having laterally opposite arm rests 104.

The assembly 10in embodiment 100 is exactly that of FIG. 2 and will not be redescribed in detail except to reaffirm the presence of the seat support member 12 and the parallelogram arms 16, 18, 20, and 22 lying along their major longitudinal lengths in a common horizontal plane. The seat assembly 10 is trimmed with a seat cushion 106 which may contain such springs and padding as are well known in the art and which may be permanently or loosely attached to the assembly 10. In addition, the backrest 68 is trimmed for comfort and appearance.

Base 102 comprises four spaced and radial legs 108 extending outwardly from a central support housing 110 and being fitted with casters 112. At the top of cylindrical housing 110 and suitably pinned thereto is a swivel cup 114'which carried atop the flange lip thereof a transversely extending support member 116 in the shape of an inverted pan. The member 116 is placed on the cup 114 in a forwardly shifted position so that the greatest portion of its lesser, longitudinal dimension is forward of the vertical centerline of housing 1 10. Member 116 carries a liaison member 120 which, in turn, carries the assembly 10 of embodiment 100.

More specifically, liaison member 120 is a forwardly raked, U-shaped member of rigid material such as sheet steel having a flat bight 122 welded to member 116 and outwardly turned flanges 124 welded to seat support member 12. The forward rake evident in FIG. 4 permits the member 120 to liaison between the base 102 and the forwardly located transverse member 12 of seat assembly 10.

As best shown in FIG. 5, the support member 116 extends out just beyond the lateral edges of assembly 10 and cushion 106 to carry closed loops 126 of fiat steel stock, the bottoms of which are longitudinally flat to rest securely on member 1 16 and the tops of which are also longitudinally flat to receive wood armrest plates 128. The armrest arrangement is completely symmetrical about a centerline of the seat and, thus, only one side is illustrated in FIG. 5. A bumper 130 of rubber or other resilient material may be placed on member 116 to prevent damage to unusually heavy load.

It is to be understood that the invention has been described with reference to an illustrative embodiment and that various modifications may be made to the invention as will be apparent to those of ordinary skill in the art. Accordingly, the foregoing description is to be construed as illustrative rather than limiting.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a seat assembly: a parallelogram-type, unison action seat comprising a seat support; a backrest sup port; first and second resilientparallelogram arms interconnecting said seat and backrest supports into a unison-action seat arrangement to permit substantially vertical, unison deflection of the rear of the seat support and the backrest support under load without substantial variation in angularity; said parallelogram arms being secured to the backrest support at vertically spaced points but lying over the greater portion of the longitudinal lengths thereof substantially in the same horizontal plane.

2. The apparatus defined in claim 1 including third and fourth parallelogram arms similarly connected between said supports and being laterally spaced from and substantially parallel to the first and second arms to define a seating area.

3. The apparatus defined in claim 2 wherein the first and third arms are formed as a continuous element having a laterally extending portion, and the second and fourth arms are formed as a continuous element having a laterally extending portion, the laterally extending portions being substantially parallel and vertically spaced.

4. The apparatus defined in claim 2 including a plurality of spring elements extending laterally between the spaced arms to define a seating area.

5. The apparatus defined in claim 4 wherein the spring elements alternately extend between the laterally outermost arms and the laterally innermost arms over the coplanar portions thereof.

6. The apparatus defined in claim 4 wherein the spring elements are sinuous wires.

7. The apparatus defined in claim 4 including a cushion disposed over the spring elements.

8. The apparatus as defined in claim 2 wherein the seat support is a substantially rigid, transversely extending plate, the assembly including base means secured to the plate for supporting the assembly relative to a load bearing surface.

9. The apparatus as defined in claim 2 wherein the backrest support is a substantially rigid transversely extending member.

10. Apparatus as defined in claim 9 wherein the backrest support includes a substantially vertical transverse portion, a substantially horizontal transverse portion, and a pair of side portions.

11. Apparatus as defined in claim 1 wherein the 16. Apparatus as defined in claim 1 wherein the seat support includes a substantially rigid transverse portion, the assembly further comprising a base including a carriage portion and a liaison portion, the liaison portion being formed as a rigid, forwardly raked, U-shaped member having outwardly turned flanges at the upper ends thereof for connection to said transverse portion.

17. Apparatus as defined in claim 16 including a transversely extending support member disposed between the base and the liaison member, and armrest means carried at the laterally opposite ends of the support member. 

1. In a seat assembly: a parallelogram-type, unison action seat comprising a seat support; a backrest support; first and second resilient parallelogram arms interconnecting said seat and backrest supports into a unison-action seat arrangement to permit substantially vertical, unison deflection of the rear of the seat support and the backrest support under load without substantial variation in angularity; said parallelogram arms being secured to the backrest support at vertically spaced points but lying over the greater portion of the longitudinal lengths thereof substantially in the same horizontal plane.
 2. The apparatus defined in claim 1 including third and fourth parallelogram arms similarly connected between said supports and being laterally spaced from and substantially parallel to the first and second arms to define a seating area.
 3. The apparatus defined in claim 2 wherein the first and third arms are formed as a continuous element having a laterally extending portion, and the second and fourth arms are formed as a continuous element having a laterally extending portion, the laterally extending portions being substantially parallel and vertically spaced.
 4. The apparatus defined in claim 2 including a plurality of spring elements extending laterally between the spaced arms to define a seating area.
 5. The apparatus defined in claim 4 wherein the spring elements alternately extend between the laterally outermost arms and the laterally innermost arms over the coplanar portions thereof.
 6. The apparatus defined in claim 4 wherein the spring elements are sinuous wires.
 7. The apparatus defined in claim 4 including a cushion disposed over the spring elements.
 8. The apparatus as defined in claim 2 wherein the seat support is a substantially rigid, transversely extending plate, the assembly including base means secured to the plate for supporting the assembly relative to a load bearing surface.
 9. The apparatus as defined in claim 2 wherein the backrest support is a substantially rigid transversely extending member.
 10. Apparatus as defined in claim 9 wherein the backrest support includes a substantially vertical transverse portion, a substantially horizontal transverse portion, and a pair of side portions.
 11. Apparatus as defined in claim 1 wherein the parallelogram arms are pivotally connected to the backrest support.
 12. Apparatus as defined in claim 1 including a backrest secured to the backrest support.
 13. Apparatus as defined in claim 12 wherein the backrest comprises a flexible, U-shaped border member having two vertical portions and a transverse portion.
 14. Apparatus as defined in claim 13 further including a plurality of spring elements extending between the backrest support and the transverse portion of said border member.
 15. Apparatus as defined in claim 14 wherein the spring elements are sinuous wires.
 16. Apparatus as defined in claim 1 wherein the seat support includes a substantially rigid transverse portion, the assembly further comprising a base including a carriage portion and a liaison portion, the liaison portion being formed as a rigid, forwardly raked, U-shaped member having outwardly turned flanges at the upper ends thereof for connection to said transverse portion.
 17. Apparatus as defined in claim 16 including a transversely extending support member disposed between the base and the liaison member, and armrest means carried at the laterally opposite ends of the support member. 